1. Field of the Invention
The present invention relates to a cell tracking device and a method for tracking a biological sample such as a cell on the basis of images of a cell image group collected using a microscope and measuring a displacement of the position of the biological sample, and a storage medium non-transitory storing computer-readable cell tracking programs.
2. Description of the Related Art
In researches in the fields of biology and medicine, for example, fluorescence and bioluminescence intensities which represent biological activity of a biological sample such as a living cell are observed, a biological sample and a bio-related substance to be examined are imaged, and variations in shape characteristics and of expression levels inside and outside the biological sample are chronologically observed. In this observation, the amount of light emitted from each individual living cell is chronologically measured in order to capture an expression level of a light-emitting gene as time passes. In the chronological measurement of the amount of light emission, time-lapse (very slow speed) imaging is performed to capture a dynamic functional expression of protein molecules in a biological sample such as a cell. This time-lapse imaging allows a time-lapse image sequence in which a plurality of time-lapse images are arranged in time series.
In measuring an amount of light emission chronologically, generally, the position of a biological sample such as a cell is visually confirmed from each image of the time-lapse image sequence, and the brightness value on the position or the average brightness within a predetermined region with the position at the center thereof or the like is plotted as an amount of light emitted from a cell.
However, the visual measurement is a very complicated operation. It is thus desirable to perform an automatic operation by a cell tracking process capable of continuing tracking a cell position with accuracy, to which an image recognition technology is applied.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2010-14964 discloses a technology corresponding to the foregoing technology of measuring a displacement of a biological sample such as a cell. The publication discloses a biological observation device that allows image pickup for detection and image pickup for observation to be performed by a single image pickup device. The biological observation device includes an objective lens disposed close to a sample, an image acquisition unit which picks up the sample through the objective lens, an objective lens driving unit which drives the objective lens in a direction to correct a displacement of the sample, and a control unit which controls the image acquisition unit to capture an observing image for observing the sample and a detecting image for detecting a displacement of the sample. The biological observation device captures the observing image by long-time exposure and captures the detecting image by short-time exposure. The biological observation device uses an image with a small subject blur which is picked up by short-time exposure in order to detect a displacement of a sample.